1. Field of the Invention
The present invention relates to an apparatus for forming a bottom stop on a continuous slide fastener chain having elements of a thermoplastic synthetic resin material interlocked with each other by melting the thermoplastic synthetic resin material by means of an ultrasonic horn at a position on the fastener chain which is adjacent to a space portion of the slide fastener chain.
2. Description of the Prior Art
A typical conventional bottom-stop forming apparatus of the type described above has been arranged such that a projection which enters a space portion of a continuous slide fastener chain is engaged with an element at the rear edge of the space portion in order to effect positioning of the fastener chain, and then a plurality of elements near the space edge portion are clamped and melted by means of an ultrasonic horn and an anvil which are provided independently of the projection, thereby forming a bottom stop. Such conventional arrangement, however, encounters the following problems: Since the anvil is provided independently of the positioning projection, there are unfavorably variations in position of the anvil with respect to the projection, which disadvantageously involves variations in position of bottom stops. Further, there is a possibility that the anvil may come in contact with the thread which is employed to attach the elements to respective strips of tape, such as to damage the thread. Moreover, since the anvil is independent of the projection, it is inconveniently difficult to allow the anvil to move while keeping it in contact with the projection. In consequence, a gap is undesirably formed between the projection and the anvil, which makes it difficult to form a bottom stop in which the elements constituting the bottom stop have completely been melted as far as the lower-most end of the fastener element rows.